Production of light.



S. O. HOFFMAN.

PRODUCTION OF LIGHT.

APPLIGATION FILED NOV. 3, 1911.

1 ,O43,009, Patented Oct. 29, 1912.

2 SHEETSSHEET 1.

S. O. HOFFMAN.

PRODUGTION'OF LIGHT.

APPLICATION FILED NOV. 3, 1911.

Patented 0013.29, 1912.

2 SHEETS-SHEET 2.

SAMUEL O. HOFFMAN, OF SAN FBANQISOO, CALIFORNIA.

PRODUCTION OF Specification of Letters Patent.

Application filed November 3, 1911. 7 Serial 1%. 858,359.

To all wlmm it may concern:

Be it known that I, SAMUEL O. Hor'FMAN, citizen of the United States, residing in the city and county of San Francisco and State of California, have invented new and useful Im rovements in Production of Light, of which the following is a specification.

This invention relates to the production of light, and pertains more especially to improvements and developments in the method and means indicated in my co-pend ing application Serial No. 638,911. While this present invention is in the nature of an improvement on the subject-matter of said prior application, it is not to be considered thereby as limited in its nature and scope, since in some respects it proceeds along distinctly original lines.

The invention consists of the parts and the construction and combination of parts as hereinafter more fully described and claimed, having reference to the accompanying drawing, in which-- Figures 1, 2 and 3 illustrate the application of the laws of optics, underlying the invention. Figs. 4: and 6 represent. different forms of the invention embodying the same principle. Figs. 5 and 7 are enlarged sec tional views taken respectively on lines 2-2, Fig. 4 and 33 Fig. 6.

In my prior application referred to, I disclose a method for separatingthe radiation from an incandescent source into its luminous and non-luminous portions, allowing the luminous portions to radiate freely and directing the non-luminous back to the source, using it over and over again regeneratively. without loss.

In the present invention I employ the principle of a spectrum; the invention consisting generally in forming a spectrum, or series of spectra of the radiation from the source directing the non-luminous portion of the spectrum or spectra back to the source, and allowing the luminous portion to pass freely; also to roduce radiation of a desired wave length y formin a spectrum or spectra of the total radiation from the source allowin the portion of the spectrum of the desire wave length to pass, and directing the remainder of the spectrum back to the source and using it regeneratively.

The radiation from an incandescent source, such as a lamp filament, consists of to have such a low efliciency. In this invention a spectrum is formed of the radiation from' the source, the luminous portion of the spectrum being allowed to pass freely,

and the non-luminous infra-red radiation, carrying most of the energy, being directed back to the source and used regeneratively; the consumption of energy thus being equivalent only to the li ht produced, and there is no production 0% useless infra-red radiation.

Fig. 1 represents diagrammatically the usual method of producing a spectrum; A narrow beam of white light D, coming from source X, enters the prism Z, and is refracted toward the base. White light consists of Waves of all lengths between the red and violet, and each wave length is refracted to an extent depending upon its length, the violet being refracted most and the red least. Therefore, the beam of white light D upon passing through the prism is split up into its constituent Wave lengths (indicated by colors) producing a spectum R V on the screen Y J. Now suppose D is a beam from an incandescent source X containing radiation of all wave lengths, luminous and nonluminous. The beam will be refracted as before and a spectrum formed on screen Y J, the luminous portion extending from V to R and infra-red R to H. It might be remarked that aside from the physiological fact of being luminous, the optical behavior of the infra-red radiation is no more diflerent from the luminous radiation than that of red light is from violet light.

Fig. 2 is exactly the same as Fig. 1 except that a sheet of glass is used in place of the screen Y J. That portion of the glass where the infra-red radiation strikes R H is silvered; R V being left clear. It is apparent then that all the infra-red radiation in the beam D will be intercepted by this silvered glass and reflected back toward the source, the luminous radiation radiating freely through the clear glass R V. If now the total radiation from the source should be passed through a structure similar to Fig. 2,

Patented 0013.29, 1912.

all the non-luminous radiation would be reflected back toward the source and only luminous radiation would be produced.

In Figs. 1 and 2, the waves of-diiferent lengths would overlap to a certain extent on Y J producing an impure spectrum. Fig. 3 shows the usual arrangement to overcome this. The radiation from the source X is intercepted by lens L and without the prism would produce a sharp image of the source at S, but if a prism Z is interposed, the light will deviate toward the base of the prism and a spectrum will be formed on Y J. This spectrum will really consist of a' series of images of the source in radiation of each wave-length, producing a spectrum with very little overlapping. It apparent that the function of the lens L and prism Z could be combined into a prism with curved faces, as shown in the prisms L in Fig. 5. These general principles are incorporated in the lamps shown in Figs. 4 to 6.

In Fi 4 is represented an incandescent electric l amp, similar to the ordinary form except as explained below. A is the outer bulb; B an inner bulb so constructed as to produce on the inner surface of bulb A. a series of spectrum images of the filament C. E is a spring support for the filament to keep it in proper'position. The bulb A is silvered where the infra-red portions of the spectra strike, and clear where the luminous portions are formed; the infra-red radiations thus being reflected back to the filament and used regeneratively, while the lu minous waves radiate freely. There is thus no loss due to non-luminous radiation.

Fig. 5 is an enlarged cross section of Fig. 4. The inner bulb B has formed on it prisms L, (here shown exaggerated) which form spectra S on the bulb A; the portion of the bulb A where the infra-red waves strike being silvered, as explained. The faces of the prisms L are curved or lenticular in order to product sharp spectrum images of .the filament; the return of the infra-red radiation to the source being accomplished by the reflector provided by the silvered portion of the bulb in conjunction with the prisms.

Fig. 6 shows another form or the lamp lettered to correspond. The inner bulb B (shown in section in Fig. 7) is so made as to produce a series of spectra at certain points on its inner surface, which is silvered where the nonluminous portions of the spectrum strike, and clear where the luminous are formed; the result being the same as in the lamp shown in Fig. 4. The inner bulb B is constructed, (Fig. 7 of a number of parabolic silvered reflecting surfaces m, m, m, which in conjunction with the prisms G (shown exaggerated) produce sharp spectrum images at points k, 7c, is, where the bulb is silvered asescribed. F is a thin X-shaped strip of 0 carbon placed between the two limbs of the filament, where it absorbs some of the re- 7 fiected infra-red radiation and acts as a secondary source. Its size is so proportioned that it will attain the same temperature as the filament. It is not necessary to connect it in the circuit any way.

It is to be noted that with the combination of prisms and reflectors shown, the spectrum image will always be formed at the same point (depending upon the curvature of the reflector), and independent of the refractive index of the glass used. The inner bulb B is made in portions of, gradually increasing diameter as shown at B B B in order to get the greatest possible amount of surface exposed to the radiation of the filament, as the life of an incandescent varies directly with the inner surface (due to blackening). In this lamp the outer bulb A has no function other than a mechanical inclosure.

The bulb B in Fig. 6 is preferably made as shown with a series of steps or conjoint sections with the lengthwise portions of these sections all parallel with the filament, in order to obtain the greatest amount of possible surface in a pear-shaped bulb, to which latter we are limited by the commer cial practice of to-day.

It is understood that any suitable method of manufacturing may be employed in constructing these lamps, one very simple method being the making of the bulbs in sections, applying or forming the necessary prismatic surfaces on the inner bulbs and then assembling the sections.

A convenient way for forming the refiec: tors with prismatic surfaces is to draw the necessary forms on an enlarged scale, then reduce and transfer the same photographically to the interior of a polished cast iron mold. The mold is then engraved with the aid of templets and in casting the glass in the mold an easily fusible glass is preferably employed while the mold itself is keptat a temperature but slightly below that of.

the solidifying point of the glass, so as to prevent chilling. In the casting operation air is exhausted from the molds and the fluid glass is forced into all the fine lines by atmospheric pressure. I

A convenient method of forming the reflecting surfaces in proper position for reflecting only those portions of the radiation which are non-luminous is to silver the entire reflecting and transparent portion of the surface of the bulb after the parts have been assembled, then coat the silvered surface witha film of biehromatized gelatin. A radiation source similar in shape and po-' -sition to the filament is then placed in the bulb and a filter interposed between the source of radiation and the reflector, which filter is so constructed as to absorb the luminous rays while allowing the infra-red rays to pass through freely. A suitable filter is formed of a solution of iodin in carbon disulfid. Since all the luminous radiation is absorbed by the filter the spectra formed will consist only of the infra-red rays, and as the bichromatized gelatin is rendered insoluble when acted upon by such infra-red on the glass. The silvering so exposed is then dissolved off, leaving these portions of the glass transparent and finally the insoluble gelatin is removed leaving the reflecting surfaces perfect on those positions where the infra-red rays will strike the same.

The insoluble portion of gelatin may be removed by simply rubbing when softened by boiling Water if the silver film is thick enough to stand it, otherwise by heating in contact with anoxidizing agent such as potassium nitrate, when the gelatin is de stroyed. (This insoluble film is transparent.) In the above process the gelatin can be made more sensitive to the infra-red radiation by the use of dyes in the well known manner.

It is apparent that by suitably s'ilvering the inner bulbs it is possible to intercept any portion or portions of thespectra formed and therefore to produce radiation of any wave length and light of any color. By this present invention I accomplish not only a selection of the desired radiation but a positive separation of the same.

It is manifest that the principle of this invention is applicable to any form of-lamp using an incandescent source of radiation.

Having thus described my invention, what I claim and desire to secure by Letters Patent is l. The method of producing light from an incandescent source, which consists in forming a spectrum of the radiation from the source directing the rays of infra-red portion of the spectrum back to the source, using such portion of the radiation regeneratively and allowing the rays of the luminous portion of the spectrum to radiate freely:

2. The method of producing radiation of desired wave length from a source emitting radiation of various Wave lengths, which consists in forming a spectrum of the radiation from the source allowing the rays of that portion of the spectrum of desired wave length to radiate freely, and directing the radiation from the remainder of the spectrum back to the source, and using said radiation regeneratively.

3. The method of producing light from an incandescent source, which consists in forming a spectrum of' the radiation from the source directing the rays of the nonluminous portion of the spectrum back to the source, using such portion ,of the radiation regeneratively, and allowing the rays of the luminous portion of the spectrum to radiate freely.

4. The method of producing luminous radiation from an incandescent source which consists of forming a spectrum of the radiation from the source, allowing theluminous portion of the spectrum to radiate freely for illuminative purposes and converting the non-luminous, longer wave length portion of the spectrum into luminous radiation'which is allowed to radiate freely for illuminative purposes.

5. The method of producing luminous radiation of desired wave length from an incandescent source emitting waves of various lengths, which consists in forming a spectrum of the radiation from an incandescent source, allowing the portion of the spectrum representing the radlation of the desired wave length to radiate freely, and converting that portion ofthe spectrum representing the radiation of longer wave length into radiation of desired wave length, and then allowing it to radiate freely in conjunction with the initial freely radiating waves.

y In testimony whereof I have hereunto set my hand in the witnesses.

- st 0. HOFF presence of two subscribing 

